I'll try and get you one, but fair warning - depending on the type of platy it's very hard to tell the difference. For example, the gravid spot on an arrowtail goes very obviously black, but a blue neon has a black gravid spot all the time...
http/images.google.com/imgres?imgurl=htt...hl%3Den%26lr%3D here is an image of a gravid spot .... My silver sailfin and the one I have now showed no spot at all .... As it was suggested before you may not see it .. don't expect too although it is quite common ... She will egt very fat or have a tiny brood (1+) and she may not get plump
Okay, I gave up trying to get a photo of my preg arrow as a comparison. So here's my non-preg arrow on the left, and the same arrow but with my bad drawing over the top on the right. Bear in mind that not all platys will have a totally black gravid spot, some will just have black circles and lines (it looks like someone's drawn on them with a felt tip)...